Dehumidifier system

ABSTRACT

A dehumidifier system ( 10 ) comprising: a dehumidifying chamber ( 12 ) into which moist air is introduced and from which less moist air is removed after dehumidification; a desiccant solution ( 28 ) situated in at least one reservoir ( 30 ); a first conduit ( 13 ) via which desiccant solution ( 28 ) is transferred from the at least one reservoir ( 30 ) to the dehumidifying chamber ( 12 ), said solution being returned to said at least one reservoir ( 30 ) after absorbing moisture from the moist air; a regenerator ( 32 ) which receives desiccant solution from said at least one reservoir and removes moisture from it; a second conduit via which desiccant is transferred from the at least one reservoir ( 30 ) to the regenerator ( 32 ), said solution being returned to said at least one reservoir after moisture is removed from it; and a heat pump ( 44 ) that transfers heat from the solution in the first conduit to the solution in the second conduit.

FIELD OF INVENTION

This invention is in the field of dehumidification and in particular isconcerned with improved efficiency of desiccant type dehumidifiers.

BACKGROUND OF INVENTION

Large scale air dehumidifying systems based on a desiccating agent areassociated with two main problems. One problem is that the dried airoutput is warmer than the moist air input. This result is caused by theheating of the air from latent heat of evaporation as the moisture isremoved therefrom and also, to a lesser degree by the heating of the airby transfer of heat from the generally warmer desiccant. A secondproblem is that regeneration of the desiccant requires considerableenergy.

Dehumidifying systems based on liquid desiccants dehumidify air bypassing the air through a tank filled with desiccant. The moist airenters the tank via a moist air inlet and dried air exits the tank via adried air outlet. In one type of desiccant system a shower of desiccantfrom a reservoir is sprayed into the tank and, as the desiccant dropletsdescend through the moist air, they absorb water from it. The desiccantis then returned to the reservoir for reuse. This causes an increase inthe water content of the desiccant.

Water saturated desiccant accumulates in the reservoir and is pumpedtherefrom to a regenerator unit where it is heated to drive off itsabsorbed water as vapor. Regenerated desiccant, which heats up in thisprocess, is pumped back into the reservoir, for reuse. Since the waterabsorption process leads to heating of the air and the regenerationprocess heats the desiccant, substantial heating of the air takes placeduring the water absorption process.

An example of a device using a circulating hygroscopic liquid such as aLiCl desiccant is described in U.S. Pat. No. 4,939,906. In this patent aboiler is provided with finned tubes for the flow of the heateddesiccant. This patent also discloses pre-heating the saturateddesiccant before it enters the boiler for final regeneration by directtransfer of heat thereto from desiccant leaving the tank.

Other variations of systems using re-circulated desiccant solutions fordehumidifying air are shown in U.S. Pat. Nos. 4,635,446, 4,691,530 and4,723,417. Many of these systems utilize transfer of heat from oneportion of the dehumidifier to another to improve its efficiency.

In general, regeneration of the liquid desiccant requires its heatingwith the concomitant expenditure of energy.

SUMMARY OF INVENTION

The present invention, in some embodiments thereof, is designed toutilize heat transfer in a new way in the process of regenerating itsliquid desiccant thereby enhancing the overall efficiency of the system.

In a preferred embodiment of the invention a heat pump extracts heatfrom liquid desiccant, preferably in a humidity collector unit andtransfers the heat to a heating coil in a regenerator unit therebyreducing the overall energy required by the system. In addition, thistransfer of energy has the effect of cooling the desiccant whichcontacts the moist air that enters the system. Thus, dry air which exitsthe system is cooler than it would be in the absence of the heattransfer.

In addition, in preferred embodiments of the invention, heat energy inone or more of moisture laden air which exits the regenerator, heateddesiccant which exits the regenerator and air which exits thedehumidifier is used to heat the desiccant to be regenerated either onits way to or in the regenerator tank.

According to an aspect of some preferred embodiment of the invention, adehumidifier is provided in which the relative humidity of treated airis self regulating, such that the relative humidity of the air exitingthe dehumidifier remains relatively constant as the temperature orhumidity of the air entering the dehumidifier drops. The air temperatureof the exiting air preferably depends on the input air conditions, withthe exit air temperature dropping with lower input_temperature/relativehumidity. There is thus provided, in accordance with a preferredembodiment of the invention, a dehumidifier system comprising:

a dehumidifying chamber into which moist air is introduced and fromwhich less moist air is removed after dehumidification;

a desiccant solution situated in at least one reservoir;

a first conduit via which desiccant solution is transferred from the atleast one reservoir to the dehumidifying chamber, said solution beingreturned to said at least one reservoir after absorbing moisture fromthe moist air;

a regenerator which receives desiccant solution from said at least onereservoir and removes moisture from it;

a second conduit via which desiccant is transferred from the at leastone reservoir to the regenerator, said solution being returned to saidat least one reservoir after moisture is removed from it; and

a heat pump that transfers heat from the solution in the first conduitto the solution in the second conduit.

Preferably, the heat pump comprises a first heat exchanger whichreceives heat from the solution in the first conduit, a second heatexchanger that receives heat from the solution in the second conduit anda compressor.

Preferably, the regenerator comprises a regenerator chamber in whichmoisture is removed from the solution by contact with air that isbrought into the chamber. Preferably, the compressor is cooled by saidair prior to its entry into the regenerator chamber, such that themoisture removal ability of the air is increased.

In a preferred embodiment of the invention, the heat pump includes anadditional heat exchanger which transfers heat from a refrigerant afterthe refrigerant leaves the second heat exchanger. Preferably, theregenerator comprises a regenerator chamber in which moisture is removedfrom the solution by contact with air that is brought into the chamber.Preferably, the additional heat exchanger is cooled by said air prior toits entry into the regenerator chamber, such that the moisture removalability of the air is increased.

In a preferred embodiment of the invention, the system includes acontrol that controls the amount of heat transferred by the heat pump.

In a preferred embodiment of the invention, the at least one reservoircomprises a first reservoir from which solution is transferred via thefirst conduit and a second reservoir from which solution is transferredvia the second conduit. Preferably, a substantial temperaturedifferential is maintained between the first and second reservoirs.

Preferably, the system includes a conduit that connects the first andsecond reservoirs, such that the level of solution in them issubstantially the same.

There is further provided, in accordance with a preferred embodiment ofthe invention, a dehumidifier system comprising:

a dehumidifying chamber into which moist air is introduced and fromwhich less moist air is removed after dehumidification;

a desiccant solution situated in a first reservoir;

a first conduit via which desiccant solution is transferred from thefirst reservoir to the dehumidifying chamber, said solution beingreturned to said at least one reservoir after absorbing moisture fromthe moist air;

a desiccant solution situated in a second reservoir;

a regenerator which receives desiccant solution from the secondreservoir and removes moisture from it;

a second conduit via which desiccant is transferred from the secondreservoir to the regenerator, said solution being returned to saidsecond reservoir after moisture is removed from it; and

wherein a substantial temperature differential is maintained between thefirst and second reservoirs.

Preferably, the system includes a conduit connecting the first andsecond reservoirs such that the level of solution in them issubstantially the same.

Preferably, the conduit provides for only limited mixing between the tworeservoirs such that the substantial temperature differential ismaintained between them. Preferably, the temperature differential is atleast 5° C., such as at least 10° C. or at least 15° C.

Preferably, the system includes means for providing an additionallimited amount of mixing between the two reservoirs.

There is further provided, in accordance with a preferred embodiment ofthe invention, an air modifying device, including:

an enclosure including apparatus for modifying air entering theapparatus via an air inlet and having an air outlet for the modifiedair;

a first conduit having an entrance for air and an exit communicatingwith the inlet;

a second conduit having an exit and an entrance communicating with theoutlet; and

a mounting surface adapted for mounting the device on a partition suchthat the enclosure is on a first side of the partition and the entranceto the first conduit and the exit from the second conduit are situatedon a second side of the partition.

Preferably, the conduits carry air from the first side of the partitionto the second side of the partition. Preferably, the mounting surface isadapted for mounting on a window sill and the system includes a sealaround the conduits that seals the first side of the partition from thesecond side of the partition when a window is closed on the conduits.

In a preferred embodiment of the invention, the apparatus for modifyingair is a dehumidifier.

In a preferred embodiment of the invention, the apparatus for modifyingair is an air conditioner including a heat pump that cools air enteringthe inlet by contact with a cold surface of the heat pump.

In a preferred embodiment of the invention, the apparatus for modifyingair is a combination dehumidifier and an air conditioner including aheat pump that cools air entering the inlet by contact with a coldsurface of the heat pump.

In a preferred embodiment of the invention, the dehumidifier is adehumidifier system as described herein.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be more clearly and fully understood from thefollowing detailed description of the preferred embodiments thereof, inwhich the same reference numerals in different drawings correspond tothe same features, read in conjunction with the drawings in which:

FIG. 1 schematically shows a dehumidifier unit, in accordance with apreferred embodiment of the invention;

FIG. 2 schematically shows a second dehumidifier unit, in accordancewith an alternative preferred embodiment of the invention;

FIG. 3 schematically shows a system for wetting a sponge with desiccantsolution, in accordance with a preferred embodiment of the invention;and

FIG. 4 shows a preferred construction for a window mounted dehumidifierunit in accordance with a preferred embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A dehumidifying system 10, in accordance with a preferred embodiment ofthe invention comprises, as its two main sections a dehumidifyingchamber 12 and a regenerator unit 32. Moist air enters dehumidifyingchamber 12 via a moist air inlet 14 and dried air exits chamber 12 via adry air outlet 16.

In a preferred embodiment of the invention, desiccant 28 is pumped by apump 20 from a desiccant reservoir 30 via a pipe 13 to a series ofnozzles 22. These nozzles shower a fine spray of the desiccant into theinterior of chamber 12, which is preferably filled with a cellulosesponge material 24 such as is generally used in the art for suchpurposes. The desiccant slowly percolates downward through the spongematerial into reservoir 30. Moist air entering the chamber via inlet 14contacts the desiccant droplets. Since the desiccant is hygroscopic, itabsorbs water vapor from the moist air and drier air is expelled throughoutlet 16. Preferably, reservoir 30 is located on the bottom of chamber12 so that the desiccant from sponge 24 falls directly into thereservoir.

In a preferred embodiment of the invention, a pump 35 and associatedmotor 37 pump desiccant from an extension of reservoir 30 into pipe 13.A divider 38 receives desiccant from pipe 13 and sends part of thedesiccant to nozzles 22 and part to regenerator unit 32. A valve orconstriction 39 (preferably a controllable valve or constriction) may beprovided to control the proportion of the desiccant which is fed toregenerator 32. If a controllable valve or constriction is used, theamount of desiccant is preferably controlled in response to the amountof moisture in the desiccant.

Chamber 34 includes a heat exchanger 36 which heats the desiccant todrive off part of the water vapor it has absorbed, thus regenerating it.

Regenerated liquid desiccant is transferred back to reservoir 30 via apipe 40 and a tube 42 of sponge material such as that which fillschamber 12. Tube 40 is preferably contained in a chamber 58 which has aninlet 60 and an outlet 62. Air, generally from outside the area in whichthe air is being modified, enters the chamber via inlet 60 and carriesaway additional moisture which is evaporated from the still hotdesiccant in tube 42, the air exiting at exit 62 carries away thismoisture and also moisture which was removed from the desiccant in theregenerator. Preferably a fan (not shown) at exit 62 sucks air fromchamber 58.

Alternatively or additionally, heat is transferred from the regeneratedliquid desiccant to the desiccant entering or in the regenerator bybringing the two desiccant streams into thermal (but not physical)contact in a thermal transfer station (not shown). Alternatively oradditionally, a heat pump may be used to transfer additional energy fromthe cooler desiccant leaving the regenerator to the hotter desiccantentering the regenerator, such that the desiccant returning to thereservoir is actually cooler than the desiccant which enters the chamber34.

In a preferred embodiment of the invention, a heat pump system 44 isprovided which extracts heat from the desiccant in reservoir 30 toprovide energy to heat exchanger 36. Preferably, this heat pump includes(in addition to exchanger 36 which is the condenser of the system) asecond heat exchanger 46 in reservoir 30, which is the evaporator of thesystem, and an expansion valve 56. This transfer of energy results in areduced temperature of the desiccant which contacts the air being driedthus reducing the temperature of the dried air. Second, this transfer ofenergy reduces the overall requirement of energy for operating theregenerator, generally by up to a factor of 3. Since the energy utilizedby the regeneration process is the major energy requirement for thesystem, this reduction in energy usage can have a major effect on theoverall efficiency of the system. Additionally, this method of heatingof the desiccant in the regenerator may be supplemented by directheating, utilizing a heating coil.

It should be understood that the proportion of water vapor in thedesiccant in reservoir 30 and in the regenerated desiccant mustgenerally be within certain limits, which limits depend on theparticular desiccant used. A lower limit on the required moisture levelis that needed to dissolve the desiccant such that the desiccant is insolution in the moisture. However, when the moisture level is too high,the desiccant becomes inefficient in removing moisture from the airwhich enters chamber 12. Thus, it is necessary that the moisture levelbe monitored and controlled. It should be noted that some desiccants areliquid even in the absence of absorbed moisture. The moisture level inthese desiccants need not be so closely controlled. However, even inthese cases the regeneration process (which uses energy) should only beperformed when the moisture level in the desiccant is above some level.

This monitoring function is generally performed by measurement of thevolume of desiccant, which increases with increasing moisture. Apreferred method of measuring the volume of liquid in the reservoir isby measurement of the pressure in an inverted vessel 50 which has itsopening placed in the liquid in the reservoir. A tube 52 leads fromvessel 50 to a pressure gauge 52. As the volume of desiccant increasesfrom the absorption of moisture, the pressure measured by gauge 52increases. Since the liquid in the chamber and in the regenerator isfairly constant, this gives a good indication of the amount of desiccantand thus of the amount of moisture entrained in the desiccant. When themoisture level increases above a preset value, the heat in chamber 34 isturned on. In a preferred embodiment of the invention, when the moisturelevel falls below some other, lower preset value, the heater is turnedoff.

Other factors which may influence the cut-in and cut-out points of theregeneration process are the temperature of the dry air, theregeneration efficiency and the heat pump efficiency. In some preferredembodiments of the invention, especially in cold air systems (as forice-skating rinks) it may be advisable to provide some direct heating ofdesiccant in the regeneration process.

In other preferred embodiments of the invention heat pumps or other heattransfer means (not shown for simplicity) are provided to transfer heatfrom the dried air exiting chamber 12 and or from the heated moist airleaving regenerator chamber 34, to heat the desiccant on its way to orin chamber 34. If heat pumps are used, the source of the heat may be ata temperature lower than the desiccant to which it is transferred.

It should be understood that cooling of the desiccant in the reservoircan result in dried air leaving the dehumidifier which has the same, orpreferably a lower temperature than the moist air entering thedehumidifier, even prior to any additional optional cooling of the dryair. This feature is especially useful where the dehumidifier is used inhot climates in which the ambient temperature is already high.

As indicated above, one of the problems with dehumidifier systems is theproblem of determining the amount of water in the desiccant solution sothat the dehumidifier solution water content may be kept in a properrange.

A dehumidifier 100, in accordance with a preferred embodiment of thepresent invention, is shown in FIG. 2. This dehumidifier is selfregulating with respect to water content of the desiccant solution andthus does not require any measurement of the volume or water content ofthe desiccant solution. Furthermore, the dehumidifier operates until apredetermined humidity is reached and then ceases to reduce thehumidity, without any controls or cut-offs.

Dehumidifier 100 is similar to dehumidifier 10 of FIG. 1, with severalsignificant differences. First, the system does not require anymeasurement of water content and thus does not have a volumetric measurefor the desiccant. However, such a measurement may be provided as asafety measure if the solution becomes too concentrated.

Second, the heat pump transfers heat between two streams of desiccantsolution being transferred from reservoir 30 (which is convenientlydivided into two portions 30A and 30B connected by pipes 30C), namely afirst stream being pumped to nozzles 22 by a pump system 130, via aconduit 102 and a second stream being pumped to regenerator unit 32 by apump system 132, via a conduit 104.

Preferably, pipes 30C (including the bypass pipes shown) are designed sothat its major effect is to generate a common level of the solution inportions 30A and 30B. In general, it is desirable that the two reservoirportions have different temperatures. This necessarily results indifferent concentrations of desiccant. However, it is consideredgenerally desirable to provide some mixing between the sections, by somepumping via the bypass pipes shown so as to transfer moisture from oneportion to the other. In a preferred embodiment of the invention atemperature differential of 5° C. or more is maintained, morepreferably, 10° C. or more and most preferably 15° C. or even more.Thus, in a preferred embodiment of the invention, reservoir portion 30Ais at a temperature of 30° C. or more and reservoir portion 30B is at atemperature of 15° C. or less.

In FIG. 2, a different construction for regenerator unit 32 is shown,which is similar to that of the dehumidifier section. Furthermore, inFIG. 2, neither section has a cellulose sponge material, which may bepresent or absent from either the embodiment of FIG. 1 or that of FIG.2.

In a preferred embodiment of the invention, applicable to either FIGS. 1or 2, spray nozzles are not used. Rather, the spray nozzles are replacedby a dripper system from which liquid is dripped on the cellulose spongeto continuously wet the sponge.

FIG. 3 shows a preferred embodiment of a dripper system for wettingsponge 24. In this system an open conduit 200, preferably in the form ofa serrated half-pipe is filled with desiccant solution 28. The desiccantsolution flow through serrations along the length of the conduit anduniformly wets the sponge. In most instances the use of a sponge,without spray is preferred since the use of a spray results indispersion of desiccant solution in the air, which must be removertherefrom. Other methods of wetting sponge 24 will occur to persons ofskill in the art and any such method may be used in the practice of theinvention.

Returning to FIG. 2, heat pump system 44 extracts heat from thedesiccant solution in conduit 102 and transfers it to the desiccant inconduit 104. Heat pump system 44 preferably contains, in addition to thecomponents contained in the embodiment of FIG. 1, an optional heatexchanger 136 to transfer some of the heat from the refrigerant leavingheat exchanger 104 to the regenerating air. Preferably, the compressoris also cooled by the regenerating air. However, when the air is veryhot, additional air, not used in the regenerator, may be used forcooling the compressor and the refrigerant. Alternatively, only such airis used for such cooling.

The resultant heating of the air entering the regenerator increases theability of the air to remove moisture from the desiccant. Heat pump 44is set to transfer a fixed amount of heat. In a preferred embodiment ofthe invention, the humidity set point is determined by controlling theamount of heat transferred between the two streams.

Consider the system shown in FIG. 2, with the air entering dehumidifierchamber 12 at 30 degrees C. and 100% humidity. Assume further that theamount of liquid removed from the air reduces its humidity to 35%without reducing the temperature. In this situation, the amount of heattransferred between the streams of desiccant solution would be equal tothe heat of vaporization of the water removed from the air, so that thetemperature of the desiccant solution falling into reservoir 20 fromchamber 12 is at the same temperature as that which enters it, exceptthat it has absorbed a certain amount of moisture from the air.

Assume further, that the regenerator is set up, such that at this sametemperature and humidity, it removes the same amount of water from thedesiccant solution. This may require an input of heat (additionally tothe heat available from the heat pump).

Further assume that the air entering the dehumidifier chamber has alower humidity, for example 80%. For this humidity, less liquid isremoved (since the efficiency of water removal depends on the humidity)and thus, the temperature of the desiccant solution leaving thedehumidifier chamber also drops. However, since less water enters thedesiccant solution from the dehumidifier chamber, the amount of waterremoved from the solution in the regenerator also drops. This results ina new balance with less water removed and the desiccant solution at alower temperature. A lower temperature desiccant results in cooler air.Thus, the temperature of the exiting air is also reduced. However, therelative humidity remains substantially the same. It should beunderstood that a reduction of input air temperature has substantiallythe same effect.

In a preferred embodiment of the invention, the system is selfregulating, with the dehumidifying action cutting off at some humiditylevel. The humidity level at which this takes place will depend on thecapacity of the solution sprayed from nozzles 22 to absorb moisture andthe ability of the solution and on the capacity of the solution sprayedfrom nozzles 22′ to release moisture.

In general as the air at inlet 14 becomes less humid (relative humidity)the dehumidifier becomes less able to remove moisture from it. Thus, thesolution is cooled on each transit through the conduit 102 and thepercentage of desiccant in the solution in 30B reaches some level.Similarly, as less moisture is removed from the air, the solution in 30Abecomes more concentrated and less moisture is removed from it (all thathappens is that it gets heated. At some point, both removal andabsorption of moisture by the solution stop since they respectivesprayed solution is stability with the air to which or from whichmoisture is transferred.

It should be understood that this humidity point can be adjusted bychanging the amount of heat transferred between the solutions inconduits 102 and 104. If greater heat is transferred, the transferability of both the dehumidifying chamber and the regenerator areincreased and the humidity balance point is lowered. For less heatpumped, a higher humidity will result. In addition, the set-point willdepend somewhat on the relative humidity of the air entering theregenerator.

FIG. 4 schematically shows a window mounted dehumidifier system 110, inaccordance with preferred embodiments of the invention. In thisembodiment, the entire unit shown in FIGS. 1 or 2 is contained in anenclosure 112 which hangs outside a window 114 of a room. Preferably,system 110 further includes a U-shaped support unit which rests onwindow sill 118 and is firmly attached to enclosure 112. Passing throughwindow 112 are two conduits, 14 and 15 corresponding to air inlet 14 anddehumidified air outlet 16 of FIGS. 1 and 2. The window closes on thetop of the conduits to seal the room from the outside. A power cord 120,plugs into a power outlet inside the window and supplies power to thedehumidifier unit. Preferably, a panel is situated inside the window onwhich controls are mounted and which provides a suitable grill for inlet14 and outlet 16. FIG. 3 also shows inlet 60 and outlet 62 used to carryaway moisture laden warm air. Additionally, inlet 60 can provide acontrollable amount of fresh air to the room.

In a further preferred embodiment of the invention the configuration ofFIG. 4 is used for a combination air conditioner and dehumidifier or fora conventional air conditioning mechanism including a heat pump thatcools air entering the inlet by contact with a cold surface of the heatpump. For an air conditioner both heat exchangers would be outside thewindow with air from the room being fed to the air conditioner'scondenser via conduit 14 and from it via conduit 16 to the room to becooled.

Units such as those shown in FIG. 4 provide for the low noise of splitair conditioning units with the convenience of window mounting.

When used in the following claims, the terms “comprise” or “include” ortheir conjugates mean “including but not necessarily limited to.”Thepresent invention has been described utilizing a preferred embodimentthereof. It should be understood that many variations of the preferredembodiment within the scope of the invention, as defined in thefollowing claims, are possible and will occur to a person of skill inthe art.

What is claimed is:
 1. A dehumidifier system comprising: a desiccantsolution situated in at least one reservoir; a dehumidifier including adehumidifying chamber into which moist air is introduced and from whichless moist air is removed after dehumidification; a first conduit viawhich desiccant solution is transferred from the at least one reservoirto the dehumidifying chamber, said solution being returned to said atleast one reservoir after absorbing moisture from the moist air; aregenerator which receives desiccant solution from said at least onereservoir and removes moisture from it; a second conduit via whichdesiccant is transferred from the at least one reservoir to theregenerator, said solution being returned to said at least one reservoirafter moisture is removed from it; a refrigeration system that comprisesa plurality of heat exchangers, a refrigerant and a compressor, whereinthe refrigerant passes through the heat exchangers, the heat exchangersincluding a first heat exchanger in thermal contact with desiccantassociated with said dehumidifier, a second heat exchanger in thermalcontact with desiccant associated with said regenerator and a third heatexchanger that is not in contact with said desiccant; and a plurality ofconduits, wherein said compressor is connected to said heat exchangersvia said conduits.
 2. A system according to claim 1 wherein the firstheat exchanger receives heat from the solution in the first conduit, andthe second heat exchanger receives heat from the solution in the secondconduit.
 3. A system according to claim 1 wherein the regeneratorcomprises a regenerator chamber in which moisture is removed from thesolution by contact with air that is brought into the chamber.
 4. Asystem according to claim 3 wherein the compressor is cooled by said airprior to its entry into the regenerator chamber, such that the moistureremoval ability of the air is increased.
 5. A system according to claim2 wherein the heat pump includes an additional heat exchanger whichtransfers heat from a refrigerant after the refrigerant leaves thesecond heat exchanger.
 6. A system according to claim 5 wherein theregenerator comprises a regenerator chamber in which moisture is removedfrom the solution by contact with air that is brought into the chamber.7. A system according to claim 6 wherein the third heat exchanger iscooled by said air prior to its entry into the regenerator chamber, suchthat the moisture removal ability of the air is increased.
 8. A systemaccording to claim 1 and including a control that controls the amount ofheat transferred between the first and second heat exchangers.
 9. Asystem according to claim 1 wherein the at least one reservoir comprisesa first reservoir from which solution is transferred via the firstconduit and a second reservoir from which solution is transferred viathe second conduit, said first reservoir forming a portion of thedehumidifier and said second reservoir forming a portion of theregenerator.
 10. A system according to claim 9 and including a conduitthat connects the first and second reservoirs, such that the level ofsolution in them is substantially the same.
 11. A system according toclaim 10 and including means for providing an additional limited amountof mixing between the two reservoirs.
 12. A system according to claim 11wherein the limited mixing results in a solution concentrationdifferential between the solution in the first and second reservoirs.13. A system according to claim 9 wherein a substantial temperaturedifferential is maintained between the first and second reservoirs. 14.A system according to claim 13 wherein the first reservoir is maintainedat a first temperature and the second reservoir is maintained at asecond temperature at least 5° C. higher than the first temperature. 15.A system according to claim 13 and including a conduit that connects thefirst and second reservoirs, such that the level of solution in them issubstantially the same.
 16. A system according to claim 15 wherein theconduit provides for only limited mixing between the two reservoirs suchsaid temperature differential is maintained between them.
 17. A systemaccording to claim 16 and including means for providing an additionallimited amount of mixing between the two reservoirs.
 18. A systemaccording to claim 16 wherein the limited mixing results in a solutionconcentration differential between the solution in the fist and secondreservoirs.
 19. A dehumidifier system comprising: a dehumidifyingchamber into which moist air is introduced and from which less moist airis removed after dehumidification; a desiccant solution, at a firsttemperature, situated in a first reservoir; a first conduit via whichdesiccant solution is transferred from the first reservoir to thedehumidifying chamber, said solution being returned to said at least onereservoir after absorbing moisture from the moist air; a desiccantsolution, at a second temperature, said second temperature being atleast 5° C. higher than the first temperature, situated in a secondreservoir; a regenerator which receives desiccant solution from thesecond reservoir and removes moisture from it; a second conduit viawhich desiccant is transferred from the second reservoir to theregenerator, said solution being returned to said second reservoir aftermoisture is removed from it.
 20. A system according to claim 19 andincluding a conduit connecting the first and second reservoirs, suchthat the level of solution in them is substantially the same.
 21. Asystem according to claim 20 wherein the conduit provides for onlylimited mixing between the two reservoirs such said temperaturedifferential is maintained between them.
 22. A system according to claim21 and including means for providing an additional limited amount ofmixing between the two reservoirs.
 23. A system according to claim 22wherein the limited mixing results in a solution concentrationdifferential between the solution in the first and second reservoirs.24. A system according to claim 19 wherein the temperature differentialis at least 10° C..
 25. A system according to claim 24 wherein thetemperature differential is at least 15° C.
 26. An air modifying deviceincluding: an enclosure including apparatus for modifying air enteringthe apparatus via an air inlet and having an air outlet for the modifiedair; a first conduit having an entrance for air and an exitcommunicating with the inlet; a second conduit having an exit and anentrance communicating with the outlet; and a mounting surface adaptedfor mounting the device on a partition such that the enclosure is on afirst side of the partition and the entrance to the first conduit andthe exit from the second conduit are situated on a second side of thepartition.
 27. A device according to claim 26 wherein the conduits carryair from the first side of the partition to the second side of thepartition.
 28. A device according to claim 27 wherein mounting surfaceis adapted for mounting on a window sill and including a seal around theconduits that seals the first side of the partition from the second sideof the partition when a window is closed on the conduits.
 29. A deviceaccording to claim 26 wherein the apparatus for modifying air is adehumidifier.
 30. A device according to claim 26 wherein the apparatusfor modifying air is an air conditioner including a heat pump that coolsair entering the inlet by contact with a cold surface of the heat pump.31. A device according to claim 26 wherein the apparatus for modifyingair is a combination dehumidifier and an air conditioner including aheat pump that cools air entering the inlet by contact with a coldsurface of the heat pump.
 32. A system according to claim 14 wherein thetemperature differential is at least 10° C.
 33. A system according toclaim 32 wherein the temperature differential is at least 15° C.
 34. Adevice according to claim 27 wherein the apparatus for modifying air isa dehumidifier.
 35. A device according to claim 27 wherein the apparatusfor modifying air is an air conditioner including a heat pump that coolsair entering the inlet by contact with a cold surface of the heat pump.36. A device according to claim 27 wherein the apparatus for modifyingair is a combination dehumidifier and an air conditioner including aheat pump that cools air entering the inlet by contact with a coldsurface of the heat pump.
 37. A device according to claim 34 whereinmounting surface is adapted for mounting on a window sill and includinga seal around the conduits that seals the first side of the partitionfrom the second side of the partition when a window is closed on theconduits.
 38. A device according to claim 33 wherein mounting surface isadapted for mounting on a window sill and including a seal around theconduits that seals the first side of the partition from the second sideof the partition when a window is closed on the conduits.
 39. A deviceaccording to claim 36 wherein mounting surface is adapted for mountingon a window sill and including a seal around the conduits that seals thefirst side of the partition from the second side of the partition when awindow is closed on the conduits.
 40. The system according to claim 3wherein the compressor is situated at an entrance to the regeneratorsection such that outside air is heated by it prior to entering theregenerator.